Method for scheduling resource, network element and user equipment

ABSTRACT

The present invention proposes a method for scheduling resource in a packet network and a network element for exchanging signaling with user equipments, wherein user equipments communicate therebetween using the resource allocated by network elements, said communication comprises talk-spurt periods during which data packets are transmitted and silent periods during which silence descriptor packets are transmitted, said method for scheduling resource comprising: said network element allocates resource for said user equipments for communication; both said user equipment and said network element detect the presence of said silence descriptor packet, and said network element determines the optimized number of resource unit(s) to be allocated to said user equipment during the interval for transmitting said data packet, based on the coding rate of said user equipment, the selected modulation coding scheme and the valid transmission times; the network element starts timing and the user equipment stops using the allocated resource if a silence descriptor packet is detected; when the timing finishes or a request for allocating resource is received from the user equipment before the end of said timing, said network element allocates the determined optimized number of resource unit(s) to said user equipment, and said user equipment begins to use said determined optimized number of resource unit(s); said network element determines the end of the interval for transmitting said data packet by detecting the silence descriptor packet; and when both said user equipment and said network element detect a silence descriptor packet, said user equipment stops using said determined optimized number of resource unit(s), while said network element releases said determined optimized number of resource unit(s).

FIELD OF THE INVENTION

The present invention relates to the field of communication, and moreparticularly to scheduling resource in a packet network.

BACKGROUND OF THE INVENTION

In recent years, due to especially higher data rate and support tomobility, broadband wireless access techniques, for example IEEE802.16e, have drawn much attention, and are competing with the existingmobile communication systems. Therefore, 3 GPP started a project of 3 Glong term evolution in 2005, to provide a better support for theincreasing requirement of operators and users with evolved accesstechnique (E-UTRA, Evolved-UTRA) and access network (E-UTRAN), in orderto achieve the object of keeping UMTS system a superior one in the next10 years or even longer time.

FIG. 1 shows the architecture of a version R7 LTE network. In such anetwork, the IP transmission is adopted between eNodeBs (EvolvedUniversal Terrestrial Radio Access Network NodeB) at lower layer, andthe eNodeBs are interconnected logically via X2 interfaces, thus forminga meshed network. Such a network architecture plan is mainly used forsupporting the mobility of user equipments (UE) within the entirenetwork, and ensuring the seamless handover of users. Each eNodeB isconnected to access gateway(s) (aGW) by means of a certain form ofmeshed connection or partly meshed connection. A eNodeB may be connectedto a plurality of aGWs, and vice versa. The LTE network employs thetechniques of OFDM, MIMO, HARQ, AMC etc. at physical layer.

In such a LTE system, there only exists packet domain, and the voicetraffic is carried via VoIP. The voice traffic is the main traffic incurrent mobile communication systems, and tends towards being carriedvia IP. VoIP traffic has certain characteristics, such as smaller packet(generally with tens of bytes), substantially fixed packet size andarrival interval of packet. For example voice packet is generatedperiodically per 20 ms during talk-spurt period and SID (silencedescriptor) packet is generated periodically per 160 ms during silentperiod.

In the downlink, OFDM may meet the requirements of data rate of 100Mbit/s and spectrum efficiency, and may implement a flexible bandwidthconfiguration from 1.25 to 20 MHz. LTE follows the concept ofHSDPA/HSUPA, i.e. obtaining a gain only by link adaptation and quickretransmission. The downlink modulation schemes of LTE include QPSK, 16QAM and 64 QAM etc..

In uplink, SC-FDMA is employed, i.e. a base station allocates a singlefrequency to a UE for transmitting user's data per TTI (transmissiontime interval), and the data of different users is separated infrequency and time, so as to ensure the orthogonality among uplinkcarriers within a cell and avoid the interference among frequencies.

At present, there are some resource scheduling methods for LTE network,such as dynamic scheduling (DS), persistent scheduling (PS) and groupscheduling (GS).

The dynamic scheduling means to schedule resource dynamically based onthe channel condition. In downlink, the eNodeB allocates resource basedon the amount of data in buffer, the channel condition etc.. In uplink,an uplink resource request message is sent first when a UE wants to senduplink data. The eNodeB allocates resource based on the received requestmessage via an uplink resource allocation message. Such a scheme has abetter resource utilization and may adjust some parameters of MCS(modulation coding scheme) adaptively based on the channel condition.But it needs more bits for the scheduling request and the resourceallocation information to achieve the adaptive adjustment, thusresulting in much signaling overhead.

If the dynamic scheduling is adopted for those smaller packets of VoIPtraffic, i.e. a request and grant signaling per TTI, the signaling loadwill be much heavier. The overhead needs to be reduced for reaching acertain VoIP user amount in the LTE system. Hence, two optimized schemesare proposed, i.e. persistent scheduling and group scheduling.

A fully persistent scheduling is similar to the circuit switchingallocation for VoIP, i.e. scheduling relatively fixed resource for thevoice traffic once for all. This persistent scheduling is advantageousbecause of the reduced or avoided L1/L2 control signaling andsimplicity. However, it has the lowest resource utilization among allscheduling methods, especially the resource unused by UE during silentperiod and unused HARP (Hybrid Automatic Repeat Request) retransmissionresource. Moreover, since the time/frequency allocation is fixed and theMCS and resource selection is fixed during the whole persistent periodconfigured when the call is set up, such a scheduling method lacksflexibility.

The group scheduling is to allocate resource from a set of resourceblocks for a group of UEs. The numbers of resource block equals to theproducts of the numbers of UE and the average activity factor. Theadvantages of such a scheduling method are improved resource utilizationand lower signaling overhead that the dynamic scheduling. However, thismethod has the following defects:

i) Difficult to manage the radio resource efficiently, especiallybecause the average activity factor is hard to be estimated, which maycause extra voice packet delay (at no resource case) or resource waste(at superfluous resource case).

ii) Lack of flexibility. Multi-rate codec will not be supportedefficiently in a group; UE switching between groups or groupreconfiguration are rather complex with a large amount of RRC (RadioResource Control) signaling. The optimal performance is achieved onlywhen the group is full, hence during the initial heating-up period theperformance of group scheduling is low.

iii) Requiring different control channel structures, e.g. BITMAPsignaling per TTI, from the normal L1/L2 control channel would berequired.

Currently, in the LTE network, a voice packet of upper layer istransmitted per 20 ms. The base station assigns 4 transmissions to a UEwithin 20 ms based on the persistent scheduling method. A general schemeis that, among the 4 transmissions, the first transmission is an initialtransmission (the transmission of the voice packet of the whole 20 ms),and the remaining 3 transmissions are used to ensure the retransmissionrequirement due to the transmission error of the first transmission.Therefore, the unused transmission resource, which is reserved forretransmission, is wasted. For the voice traffic of lower rate, theaverage retransmission is less than 1 time, thus the reserved resourcebeing wasted at least 2 times per 20 ms.

To make efficient use of the HARQ retransmission resource during thetalk-spurt period, there is a need to find a trade-off between improvingresource utilization and decreasing signaling overload.

SUMMARY OF THE INVENTION

To solve the above problem in the prior art, according to a aspect ofthe present invention, a method for scheduling resource in a packetnetwork is proposed, wherein user equipments communicate therebetweenusing the resource allocated by network elements, said communicationcomprises talk-spurt periods during which data packets are transmittedand silent periods during which silence descriptor packets aretransmitted, the method comprises: said network element allocatesresource for said user equipments for communication; both said userequipment and said network element detect the presence of said silencedescriptor packet, and said network element determines the optimizednumber of resource unit(s) to be allocated to said user equipment duringthe interval for transmitting said data packet, based on the coding rateof said user equipment, the selected modulation coding scheme and thevalid transmission times; the network element starts timing and the userequipment stops using the allocated resource if a silence descriptorpacket is detected; when the timing finishes or a request for allocatingresource is received from the user equipment before the end of saidtiming, said network element allocates the determined optimized numberof resource unit(s) to said user equipment, and said user equipmentbegins to use said determined optimized number of resource unit(s); saidnetwork element determines the end of the interval for transmitting saiddata packet by detecting the silence descriptor packet; and when bothsaid user equipment and said network element detect a silence descriptorpacket, said user equipment stops using said determined optimized numberof resource unit(s), while said network element releases said determinedoptimized number of resource unit(s).

According to another aspect of the present invention, a network elementfor exchanging signaling with user equipments is proposed, wherein saiduser equipments communicate therebetween using the resource allocated bysaid network element, said communication is based on packet switchingand comprises talk-spurt periods during which data packets aretransmitted and silent periods during which silence descriptor packetsare transmitted, the network element comprises: a detection means fordetecting the presence of said data packet or said silence descriptorpacket when said user equipments are communicating therebetween; aresource unit determination means for determining the optimized numberof resource units to be allocated to said user equipment during theinterval for transmitting said data packet, based on the coding rate ofsaid user equipment, the selected modulation coding scheme and the validtransmission times; a resource units allocation means for allocating thedetermined optimized number of resource units to said user equipmentupon the expiration of the timer for the interval for transmitting saidsilence descriptor packet or the reception of a request for allocatingresource from the user equipment before the expiration of said timer; atimer adapted to start timing when said silence descriptor packet isdetected to determine the end of said interval for transmitting saidsilence descriptor packet; and a state transition control means forchanging said network element from a talk-spurt state to a silent statewhen it detects said silence descriptor packet, or changing said networkelement from the silent state to the talk-spurt state when it detectssaid data packet.

According to yet another aspect of the present invention, a userequipment is proposed, wherein said user equipment communicates withother user equipments using the resource allocated by network elements,said communication is based on packet switching and comprises talk-spurtperiods during which data packets are transmitted and silent periodsduring which silence descriptor packets are transmitted, the userequipment comprising: a detection means for detecting the presence ofsaid silence descriptor packet or said data packet when said userequipment is communicating; and a state transition control means forchanging said user equipment from a talk-spurt state to a silent statewhen it detects said silence descriptor packet, or changing said userequipment from the silent state to the talk-spurt state when it detectssaid data packet.

BRIEF DESCRIPTION OF THE DRAWINGS

These and many other features and advantages of the present inventionwill become apparent from the following description of the embodimentsof the present invention with reference to the drawings, wherein:

FIG. 1 shows the architecture of a LTE network;

FIG. 2 is a flowchart of the method for scheduling resource according toan embodiment of the present invention;

FIG. 3 further illustrates the method for scheduling resource accordingto the embodiment of the present invention;

FIG. 4 illustrates how the UE is synchronized in state with the eNodeB;

FIG. 5 is a block diagram of the network element according to anembodiment of the present invention;

FIG. 6 is a block diagram of the UE according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention proposes a method for semi-persistently schedulingresource for data packet using retransmission statistics during thetalk-spurt periods in a packet network. With reference to FIG. 2, themethod for scheduling resource according to an embodiment of the presentinvention is described. This method may be applied to the system shownin FIG. 1. The description of the above system will not be repeatedherein.

As shown in FIG. 2, firstly, in step 201, the network element allocatesresource for the UE for communication. Herein, the network element maybe for example the eNodeB shown in FIG. 1. In the present embodiment,any existing and future solution may be adopted for allocating resource,for example, but not exclusively eNodeB allocating resource to UEs bymeans of the above-mentioned persistent scheduling method.

In step 202, both the user equipment and the eNodeB detect if a SIDpacket is present, and the eNodeB determines the optimized number ofRU(s) to be allocated to the UE during the interval for transmitting thedata packet, based on the coding rate of the UE, the selected modulationcoding scheme and the valid transmission times. The detection of saiddata packet may be performed for example by a detection means installedin the eNodeB. It should be noted that since the SID packet and the datapacket such as a VoIP packet are encapsulated by RTP (Real-timeTransport Protocol), RTP identifies at the corresponding indicator inthe header of RTP to distinguish between SID packet and data packet.Furthermore, since the SID packet is relatively small (tens of bits)while the data packet has at least more than 100 bits (256 bits for 12.2kbps), they could also be distinguished from the size of packet.Therefore, the SID packet and the data packet could be identified at thePDCP packet data convergence sub-layer.

According to a preferred embodiment of the present invention, thedetermination of the optimized number of RU(s) to be allocated to the UEmay be implemented as follows. Firstly, the power control module of theeNodeB controls the transmission power of the UE. Next, the eNodeBpre-estimates a valid SINR (Signal to Interference and Noise Ratio)based on the transmission power of the UE, and then selects a MCS(Modulation Coding Scheme), for example QPSK½, QPSK⅓, QPSK⅔ or QPSK¾etc. Finally, the eNodeB determines the number of RU(s) to be allocatedto the UE, based on the VoIP coding rate of the UE (for example, 12.2kbps), the modulation coding scheme which is selected by the eNodeBusing the signal to interference and noise ratio calculated based on thesignals received from the UE and the valid transmission times which iscalculated as a function of the UE's historical BLER (Block Error Rate)deduced by the eNodeB using statistics, thus obtaining an optimizednumber of RUs. For example, assume that the UE's VoIP coding rate is12.2 kbps, then 40 bytes (or 320 bits) are required to transmit a VoIPvoice packet at the physical layer. Assume that the selected modulationcoding scheme is QPSK½ corresponding to 144 bits, then in theconventional case, this requires 3 RUs (ceiling (320/144)) fortransmitting the whole 320 bits of a VoIP voice packet at a time. Assumethat there are 5 HARQ processes, and the TTI is 1 ms, then a HARQprocess has 4 times of transmission within 20 ms (20 ms/1 ms/5). If 3RUs are required, as described above, and 2 times of transmission aresuccessful, that is to say the number of valid transmission is 2, then12 RUs are required in total (3×4), thus the following 2 times oftransmission are wasted, i.e. 6 RUs (3×2). However, such a waste couldbe avoided by using the method according to the present invention. Theoptimized number of RUs may be expressed as:

N=the optimized number of RUs=ceiling (ceiling (x/y)/z)

Where x is the number of bits of physical layer corresponding to theVoIP coding rate, which is herein 320 bits, y is the number of bitscarried by one RU corresponding to the modulation coding scheme, whichis herein 144 bits, and z is the average valid transmission times within20 ms. Z is also a function of the block error rate, and may beexpressed as z=f (BLER). Hence, the above formula is written asN=ceiling (ceiling (320/144)/2)=(3/2)=2. It can be therefore seen that,two RUs are used to transmit while one RU is saved, and with the samevalid transmission times 2, 8 RUs are used for the 4 times oftransmission in which 2 RUs are wasted. Since the average number ofvalid transmission (z) is greater than 1, the optimized number of RUs iscertainly reduced. In this way, in comparison with those conventionalmethods, the present method improves the utilization of resource, andtherefore the saved resource (12−8=4) may be allocated to other users.Moreover, in a case in which the data delay (buffer area) on the UEincreases or the quality of the channel used by the user degrades, theeNodeB may adopt temporarily the dynamic scheduling so as to allocateadditional RUs to the UE, which is (are) generally 1 or 2 RU(s), but theeNodeB may decide the number of RU(s) to be added according topractical, situation.

Then, in step 203, the eNodeB starts timing and the user equipment stopsusing the allocated resource upon the detection of a SID packet. Saidtiming may be performed for example by a timer installed in the eNodeB.For example, a timing interval of 160 ms may be set for the timer, whichmay be longer due to the processing time concerned at physical layer,thus the end of the interval for transmitting the SID packet beingdetermined when the timing finishes.

Next, in step 204, when the timing in step 202 finishes or a resourcerequest is received from the UE before the end of said timing, theeNodeB allocates the determined optimized number of RU(s) to the UE, andthe UE stops using the allocated resource and begins to use thedetermined optimized number of resource unit(s). Then, in step 205, theeNodeB determines the end of the interval for transmitting the datapacket by detecting the SID packet. Finally, in step 206, once theeNodeB and the UE detect a SID packet, the UE stops using the determinedoptimized number of resource unit(s), while the eNodeB releases thedetermined optimized number of RU(s).

FIG. 3 further illustrates the method for scheduling resource accordingto the embodiment of the present invention. It can be seen from FIG. 3that, less than 2 RUs are used among 4 RUs in the conventional case, butwith the optimizing method according to the present invention, thereduced RU(s) is(are) utilized substantially while the transmissionpower required by the UE is economized.

It should be noted that, in the LTE network, the minimal allocation unitthat the eNodeB allocates resource to the UE is 1 RU (resource unit),and the allocation unit of transmission power of the UE is RU (known asTxPSD). In the case of the same unit transmission power, the less thenumber of RUs, the lower the transmission power required by the UE. Assuch, in the case that the UE's transmission power is limited, the lessthe number of RUs allocated to the user, the higher the UE's unittransmission power could be, thus a user is able to communicate with abase station at a farther location.

It should be appreciated that, the UE may make use of the allocatedresource substantially by employing the method of the presentembodiment, via the optimized modulation coding scheme and RUsselection. The reduction of the number of RUs to be allocated to the UEsaves the UE's transmission power, while the QoS of the UE at the borderof a cell is improved for a power-limited system, thus increasing thecoverage of the cell. Moreover, there is no need to increase the grantsignaling cost by adopting the persistent scheduling method during thetalk-spurt period. There is also no need to add new L1/L2 signaling bydetecting automatically the data packet at the eNodeB side. In order toimprove flexibility (e.g. supporting adaptive HARQ), the eNodeB canstill use dynamic scheduling grant to override the persistent schedulingduring the talk-spurt period.

To save signaling cost, the method of the present embodimentsynchronizes implicitly the UE and the eNodeB using grantsynchronization state, to avoid resource allocation conflict amongdifferent UEs. This synchronization scheme makes eNodeB unnecessary tosend a signaling to stop the last persistent grant. FIG. 4 illustrateshow the UE is synchronized in state with the eNodeB.

It can be seen from FIG. 4 that, each UE has two states. One istalk-spurt state in which the UE is in talk-spurt period, the other isSID state in which the UE is in silence period. A state transition meanstransition from the state before receiving trigger event to the stateafter executing actions. The format description of state transition maybe for example “Trigger event/Action 1, action 2, and so on aftertriggering”, such as “SID packet/stop persistent scheduling” which meansstopping the last persistent scheduling grant after receiving SIDpacket. “SID packet/stop persistent scheduling, start timer for next PSgrant” means that the eNodeB stops the last persistent scheduling grantafter receiving SID packet, then starts a timer to trigger a schedulerof eNodeB to generate a new persistent scheduling grant by the end of160 ms. “Data packet/data request” means generating a data request afterreceiving date packet for triggering a scheduler of UE to send aresource request to the eNodeB, and transit its state. It can be seenfrom the figure that, when a UE in the SID state detects a data packet,the UE sends a resource allocation request to an eNodeB which allocatesnew resource for the UE immediately upon receiving said request.Moreover, in a case in which the data delay (buffer area) on the UEincreases or the quality of the channel used by the user degrades, theeNodeB may adopt temporarily the dynamic scheduling (DS Grant in talkstate) so as to allocate additional RU(s) to the UE, which is (are)generally 1 or 2 RU(s), but the eNodeB may decide the number of RU(s) tobe added according to practical situation.

Thereby, the signaling overhead is reduced greatly by synchronizing UEwith eNodeB to avoid resource allocation conflict among different UEs.Based on the same inventive concept, according to another aspect of thepresent invention, a network element is proposed for exchangingsignaling with the UEs. The network element will be described in thefollowing with reference to FIG. 5.

FIG. 5 is a block diagram of the network element 500 according to anembodiment of the present invention, which is for example an eNodeB. Thenetwork element 500 also includes a detection means 501, a resource unitdetermination means 502, a resource unit allocation means 503, a timer504 and a state transition control means 505. When the UEs arecommunicating with each other, detection means 501 detects the presenceof the data packet or SID packet. Meanwhile, said resource unitdetermination means 502 determines the optimized number of resourceunits to be allocated to the UE during the interval for transmittingsaid data packet, based on the coding rate of said UE, the selectedmodulation coding scheme and the valid transmissions. Upon receiving UEtalk request or expiration of the timer for SID interval, the resourceunit allocation means 503 allocates the determined optimized number ofresource units to said UE. Meanwhile, upon detection of the SID packet,timer 504 starts timing to determine the end of the interval fortransmitting the SID packet. In the present embodiment, the timingperiod of the timer 504 may be set as 160 ms. When the timer 504 startstiming, the network element 500 releases the allocated resource units,and when the timer 504 finishes timing, the network element 500reallocates new optimized resource to the UE for example by thepersistent scheduling method. Referring to FIG. 4 again, the statetransition control means 505 is used for transiting the network elementfrom the talk-spurt state to the SID state, and vice versa. The statetransition is triggered by the trigger event as shown in FIG. 4. Theresource scheduling grant for the UE is stopped when a SID packet isdetected by the detection means 501, and the timer 504 starts timing.The network element 500 allocates new optimized resource for the UE,when the timer 504 finishes its timing, or when the UE requests thenetwork element 500 to allocate resource to it before the finish oftiming.

In implementation, the network element 500 of this embodiment as well asthe detection means 501, the resource unit determination means 502, theresource unit allocation means 503, the timer 504 and the statetransition control means 505, may be implemented in software, hardwareor a combination of them. For example, those skilled in the art arefamiliar with a variety of devices which may be used to implement thesecomponents, such as micro-processor, micro-controller, ASIC, PLD and/orFPGA etc.. The detection means 501, the resource unit determinationmeans 502, the resource unit allocation means 503, the timer 504 and thestate transition control means 505 of the present embodiment may beeither implemented as integrated into the network element 500, orimplemented separately, and they may also be implemented separatelyphysically but interconnected operatively.

In operation, the network element for exchanging signaling with UEs ofthe embodiment illustrated in connection with FIG. 5, may improve theresource utilization of the UEs via an optimized modulation codingscheme and RUs selection. The reduction of the RUs to be allocated tothe UE saves the UE's transmission power, while the QoS of the UE at theborder of a cell is improved for a power-limited system, thus increasingthe coverage of the cell. Moreover, there is no need to increase thegrant signaling cost by adopting the persistent scheduling method duringthe talk-spurt period. There is also no need to add new L1/L2 signalingby detecting automatically the data packet at the eNodeB side.

Based on the same inventive concept, according to yet another aspect ofthe present invention, a user equipment is proposed. The user equipmentwill be described in the following with reference to FIG. 6.

FIG. 6 is a block diagram of the UE 600 according to an embodiment ofthe present invention. The UE 600 includes a detection means 601 and astate transition control means 602. The detection means 601 is used fordetecting the presence of SID packet or data packet when the UE iscommunicating. The state transition control means 602 is used fortransiting the UE from talk-spurt state to SID state, and vice versa.The state transition is triggered by a trigger event as shown in FIG. 4.When the detection means 601 detects a SID packet, the UE stops usingthe optimized resource allocated by the network element. When thedetection means 601 detects a data packet while the UE is in silentstate, the UE sends a request for allocating resource to the networkelement.

In implementation, the UE 600 of this embodiment as well as thedetection means 601 and the state transition control means 602 itincludes, may be implemented in software, hardware or a combination ofthem. For example, those skilled in the art are familiar with a varietyof devices which may be used to implement these components, such asmicro-processor, micro-controller, ASIC, PLD and/or FPGA etc..

In operation, said UE of the embodiment illustrated in connection withFIG. 6, may improve the resource utilization without increasingsignaling cost, by detecting automatically the presence of SID packet ordata packet both at UE and at eNodeB, by employing the persistentscheduling and synchronizing the states of UE and eNodeB, and byreallocating the saved resource of UE during the talk-spurt period toother UEs.

Although the exemplary embodiments of the method for scheduling resourceand the network element for exchanging signaling with UEs of the presentinvention are described above in detail, the above embodiments are notexhaustive, and those skilled in the art can make numerous changes andmodifications within the spirit and scope of the present invention.Therefore, the present invention is not limited to those embodiments,the scope of which is defined only by the appended claims.

1. A method for scheduling resource in a packet network, wherein userequipments communicate therebetween using the resource allocated by anetwork element, said communication comprises talk-spurt periods duringwhich data packets are transmitted and silent periods during whichsilence descriptor packets are transmitted, the method comprising: saidnetwork element allocates resource for said user equipments forcommunication; both said user equipment and said network element detectthe presence of said silence descriptor packet, and said network elementdetermines the optimized number of resource unit(s) to be allocated tosaid user equipment during the interval for transmitting said datapacket, based on the coding rate of said user equipment, the selectedmodulation coding scheme and the valid transmission times; the networkelement starts timing and the user equipment stops using the allocatedresource upon the detection of a silence descriptor packet; when thetiming finishes or a request for allocating resource is received fromthe user equipment before the end of said timing, said network elementallocates the determined optimized number of resource unit(s) to saiduser equipment, and said user equipment begins to use said determinedoptimized number of resource unit(s); said network element determinesthe end of the interval for transmitting said data packet by detectingthe silence descriptor packet; and when both said user equipment andsaid network element detect a silence descriptor packet, said userequipment stops using said determined optimized number of resourceunit(s), while said network element releases said determined optimizednumber of resource unit(s).
 2. The method according to claim 1, whereinsaid silence descriptor packet is transmitted once per 160 ms duringsaid silent period, and said data packet is transmitted once per 20 msduring said talk-spurt period.
 3. The method according to claim 1,wherein if there is no delay, then the period of said timing is set as160 ms.
 4. The method according to claim 1, wherein said modulationcoding scheme is selected by said network element using the signal tointerference and noise ratio calculated based on the signals receivedform said user equipment.
 5. The method according to claim 1, whereinsaid modulation coding scheme comprises QPSK½, QPSK ⅓, QPSK ⅔, and QPSK¾.
 6. The method according to claim 1, wherein said valid transmissiontimes is calculated as a function of the user equipment's historicalblock error rate deduced by said network element using statistics. 7.The method according to claim 1, wherein said network element allocatesadditional resource to the user equipment in the case of delay.
 8. Anetwork element for exchanging signaling with user equipments, whereinsaid user equipments communicate therebetween using the resourceallocated by the network element, said communication is based on packetswitching and comprises talk-spurt periods during which data packets aretransmitted and silent periods during which silence descriptor packetsare transmitted, the network element comprising: detection means fordetecting the presence of said data packet or said silence descriptorpacket when said user equipments are communicating therebetween;resource unit determination means for determining the optimized numberof resource unit(s) to be allocated to said user equipment during theinterval for transmitting said data packet, based on the coding rate ofsaid user equipment, the selected modulation coding scheme and the validtransmission times; resource unit(s) allocation means for allocating thedetermined optimized number of resource unit(s) to said user equipmentupon the expiration of the timer for the interval for transmitting saidsilence descriptor packet or the reception of a request for allocatingresource from the user equipment before the expiration of said timer;timer adapted to start timing when said silence descriptor packet isdetected to determine the end of said interval for transmitting saidsilence descriptor packet; and state transition control means forchanging said network element from a talk-spurt state to a silent statewhen it detects said silence descriptor packet, or changing said networkelement from the silent state to the talk-spurt state when it detectssaid data packet.
 9. The network element according to claim 8, whereinsaid silence descriptor packet is transmitted once per 160 ms duringsaid silent period, and said data packet is transmitted once per 20 msduring said talk-spurt period.
 10. The network element according toclaim 8, wherein when said network element changes from said talk-spurtstate to said silent state, it stops the resource scheduling grant forsaid user equipment, and said timer start timing; and when said networkelement changes from said silent state to said talk-spurt state, itallocates new optimized number of resource unit(s) for said userequipment.
 11. The network element according to claim 8, wherein theperiod of said timing is 160 ms if there is no delay.
 12. The networkelement according to claim 8, wherein said modulation coding scheme isselected by said network element using the signal to interference andnoise ratio calculated based on the signals received form said userequipment.
 13. The network element according to claim 8, wherein saidmodulation coding scheme comprises QPSK½, QPSK ⅓, QPSK ⅔, and QPSK ¾.14. The network element according to claim 8, wherein said validtransmission times is calculated as a function of the user equipment'shistorical block error rate deduced by said network element usingstatistics.
 15. The network element according to claim 8, wherein saidnetwork element allocates additional resource to the user equipment inthe case of delay.
 16. A user equipment, wherein said user equipmentcommunicates with other user equipments using the resource allocated bynetwork elements, said communication is based on packet switching andcomprises talk-spurt periods during which data packets are transmittedand silent periods during which silence descriptor packets aretransmitted, the user equipment comprising: detection means fordetecting the presence of said silence descriptor packet or said datapacket when said user equipment is communicating; state transitioncontrol means for changing said user equipment from a talk-spurt stateto a silent state when it detects said silence descriptor packet, orchanging said user equipment from the silent state to the talk-spurtstate when it detects said data packet.
 17. The user equipment accordingto claim 16, wherein said silence descriptor packet is transmitted onceper 160 ms during said silent period, and said data packet istransmitted once per 20 ms during said talk-spurt period.
 18. The userequipment according to claim 16, wherein when said user equipmentchanges from said talk-spurt state to said silent state, it stops usingthe optimized number of resource unit(s) allocated by said networkelement, and when said user equipment changes from said silent state tosaid talk-spurt state, it sends a request for allocating resource tosaid network element